Commit 800d4d30 authored Feb 20, 2011 by Yong Zhang Committed by Ingo Molnar Feb 23, 2011

sched, autogroup: Stop going ahead if autogroup is disabled



when autogroup is disable from the beginning,
sched_autogroup_create_attach()
  autogroup_move_group()                    <== 1
    sched_move_task()                       <== 2
      task_move_group_fair()
        set_task_rq()
          task_group()
            autogroup_task_group()

We go the whole path without doing anything useful.

Then stop going further if autogroup is disabled.

But there will be a race window between 1 and 2, in which
sysctl_sched_autogroup_enabled is enabled. This issue
will be toke by following patch.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <1298185696-4403-4-git-send-email-yong.zhang0@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 1747b21f

kernel/sched_autogroup.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -161,11 +161,15 @@ autogroup_move_group(struct task_struct p, struct autogroup ag)

		p->signal->autogroup = autogroup_kref_get(ag);

		if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
		goto out;

		t = p;
		do {
		sched_move_task(t);
		} while_each_thread(p, t);

		out:
		unlock_task_sighand(p, &flags);
		autogroup_kref_put(prev);
		}

kernel/sched_autogroup.h

+5 −0

Original line number	Diff line number	Diff line
		#ifdef CONFIG_SCHED_AUTOGROUP

		struct autogroup {
		/*
		* reference doesn't mean how many thread attach to this
		* autogroup now. It just stands for the number of task
		* could use this autogroup.
		*/
		struct kref kref;
		struct task_group *tg;
		struct rw_semaphore lock;